In general, a digital TV is a device that receives a digital broadcast signal transmitted from a broadcasting station through an internal or external set-top box, processes an image of the received digital broadcast signal and outputs the processed image through a screen.
This digital TV is considered to be an indispensable device for broadcast viewing, because analog broadcasting and digital broadcasting exist together at present, but broadcasting systems will be limited to only the digital broadcasting in future.
The digital TV can output an image and sound by itself. However, in the case of independently outputting an audio signal of a multichannel, such as a 5.1 channel, supported by a video/audio medium (for example, a digital versatile disc (DVD)) or broadcast program, the digital TV cannot express the original sound quality of the audio signal as it is, due to limitations in the number and spatial locations of speakers therein. For this reason, provided that the user pursues high picture quality and high sound quality as in a theater, he/she will construct and use a home theater by connecting a separate DVD player, separate 5.1 channel speaker, separate amplifier, etc. to the digital TV.
Hereinafter, the configuration of a conventional digital TV will be described with reference to FIG. 1.
FIG. 1 schematically shows an example of the construction of a conventional home theater including a digital TV.
As shown in FIG. 1, the conventional home theater includes an external device 10, digital TV 20, and speaker system 30.
The external device 10 may be an AV device such as a DVD player, and provides a digital video signal and digital audio signal stored on a DVD to the digital TV 20.
The speaker system 30 is a device that amplifies and outputs a digital audio signal outputted from the digital TV 20. This speaker system 30 may be a multichannel speaker such as a 5.1 channel speaker and have an amplifier added as needed.
The digital TV 20 includes an HDMI receiver 21 for separating a digital video signal and a digital audio signal from a signal inputted through an HDMI cable connected with the external device 10, a switch 22 for selecting one of a digital audio signal inputted through a Sony/Philips Digital Interface (S/PDIF) cable and the digital audio signal separated by the HDMI receiver 21, a memory 23 for storing Extended Display Identification Data (EDID) information defining display parameters and characteristics of the digital TV, a main controller 25 for controlling the HDMI receiver 21 and switch 22, and a power supply 24 for supplying an operating voltage to each component of the digital TV.
Here, an illustration and description of a video signal processing-related configuration, not associated with the present invention, will be omitted.
The digital TV 20 can receive a digital video signal and digital audio signal from the external device 10 through an HDMI cable or Digital Visual Interface (DVI) and SI PDIF cables.
That is, the digital TV 20 receives the digital video signal through the DVI cable and the digital audio signal through the S/PDIF cable, which is a home digital interface standard, respectively, or receives both the digital video signal and digital audio signal through the HDMI cable.
As is well known in the art, the HDMI is an interface that transmits a digital video signal and digital audio signal, conventionally transmitted separately in DVI and SI PDIF manners, through one cable without compressing them.
A description will hereinafter be given of an external device audio signal processing operation of the conventional digital TV with the above-stated configuration.
The user can insert a DVD or compatible compact disc (CD) into the external device 10 and appreciate a movie or listen to music.
For the purpose of listening to music, the user inserts a CD or DVD containing a music file into the external device 10 and pushes a play button of the external device 10.
The external device 10, using an HDMI transmitter, packetizes an audio signal and outputs the resulting packet to the digital TV 20 through an HDMI cable. In the case where the external device does not support the HDMI, it outputs the audio signal through a separate S/PDIF cable.
Under the condition that the digital TV 20 is powered on, the HDMI receiver 21 receives the packet from the external device 10, separates the audio signal from the received packet and outputs the separated audio signal to the switch 22.
Then, the main controller 25 determines that the audio signal is present in the packet received by the HDMI receiver 21 and controls the switch 22 to form a signal path between the HDMI receiver 21 and the speaker system 30.
On the other hand, when the main controller 25 determines that no audio signal is present in the packet received by the HDMI receiver 21, it controls the switch 22 to form a signal path between the S/PDIF cable and the speaker system 30.
The speaker system 30 amplifies the audio signal inputted through the HDMI receiver 21 or S/PDIF cable and outputs the amplified audio signal through a multi-speaker so that the user can listen to music.
However, the above-mentioned conventional digital TV employs an HDMI protocol that is a standard for control of an external device, such as an AV device, connected to the TV via the HDMI cable. For this reason, the digital TV checks HDMI equipment connected therewith using an HDMI input key (hotkey) and provides only basic control functions, namely, simple functions such as input switching and ON/OFF control for the HDMI equipment. In other words, the conventional digital TV has a disadvantage in that it cannot provide more various functions.